For a hydrophobic associated polymer, a small amount of hydrophobic groups are introduced to copolymer molecular chains, such that the solution of the hydrophobic associated polymer has efficient viscosifying property, excellent salt resistance, and better temperature resistance and shear resistance, and is widely applied to increase a recovery rate and perform acid fracturing for an oilfield. However, for a high temperature and high salinity reservoir, the temperature resistance and salt resistance of the hydrophobic associated polymer still need to be improved.
For a two-tailed hydrophobic monomer containing a long-chain alkyl group and a benzene ring (Wu Xiaoyan et al. A Surface-active Two-tailed Hydrophobic Associated Acrylamide Copolymer. Guangdong Chemical Industry, 2014, 41(22): 42-44; Pu Wanfen et al. Synthesis and Property Evaluation of Two-tailed Acrylamide Type Hydrophobic Associated Polymer. Modern Chemicals, 2016(4):117-120), by the introduction of the benzene ring, the temperature resistance and hydrolysis resistance of the polymer are effectively improved; by the introduction of the long-chain alkyl group, the hydrophobic association effect of the polymer is improved favorably; a main structure of acrylamides is adopted to make the hydrophobic monomer easy to polymerize with main monomer acrylamide; the two-tailed structure effectively improves the hydrolysis resistance and hydrophobic association effect of the hydrophobic monomer. Therefore, the synthesized hydrophobic associated polymer achieves the purposes of resistance to heat, salt and hydrolysis.
Sulfonate betaine monomer is a kind of polymerizable functional monomer which contains equal number of quaternary ammonium cations and sulfonate anions and is not easily affected by pH and inorganic electrolytes. The molecules of the sulfonate betaine monomer are electrically neutral and have good chemical thermal stability and strong hydration capabilities, and copolymers of the sulfonate betaine monomer exhibit an obvious anti-polyelectrolyte behavior. In 2002, LOWE A B et al. found that polybetaine had short-range attraction and remote repulsion, and the apparent viscosity of an aqueous solution of the polybetaine increased with the increase of the concentration of external electrolyte (such as NaCl), showing an obvious anti-polyelectrolyte behavior, such that the polymer has better salt resistance. In 2012, Ding Wei, et al. used 3-(dimethylamino propyl acrylamide) propanesulfonate to copolymerize with acrylamide to obtain a copolymer P(ΔM-DMAPAAS) whose viscosity in saline water is higher than that in distilled water and whose viscosity in a salt solution containing divalent ions (Mg2+ or Ca2+) is larger than that in a monovalent ion salt solution (Na+ or K+) and increases with the increase of the salinity of the solution. In 2015, Chen Hong, et al. used acrylamide as a main monomer, allyl long-chain alkyl quaternary ammonium salt as a hydrophobic monomer, and sulfonate betaine as a functional monomer to perform terpolymerization to produce the sulfonate betaine type hydrophobic associated polymer which has temperature resistance and salt resistance properties and still has higher viscosity at 85° C.